1. Field of the Invention
The present invention relates to movable body drive methods and movable body drive systems, and pattern formation methods and pattern formation apparatuses, and more particularly, to a movable body drive method and a movable body drive system that drives a movable body substantially along a two-dimensional plane, and a pattern formation method using the movable body drive method and a pattern formation apparatus equipped with the movable body drive system.
2. Description of the Background Art
Conventionally, in a lithography process for manufacturing electron devices (microdevices) such as semiconductor devices (such as integrated circuits) and liquid crystal display devices, exposure apparatuses such as a projection exposure apparatus by a step-and-repeat method (a so-called stepper) and a projection exposure apparatus by a step-and-scan method (a so-called scanning stepper (which is also called a scanner) are mainly used.
However, the surface of a wafer serving as a substrate subject to exposure is not always flat, for example, by undulation and the like of the wafer. Therefore, especially in a scanning exposure apparatus such as a scanner and the like, when a reticle pattern is transferred onto a shot area on a wafer by a scanning exposure method, positional information (surface position information) related to an optical axis direction of a projection optical system of the wafer surface is detected at a plurality of detection points set in an exposure area, for example, using a multiple point focal point position detection system (hereinafter also referred to as a “multipoint AF system”) and the like, and based on the detection results, a so-called focus leveling control is performed (refer to, for example, Kokai (Japanese Patent Unexamined Application Publication) No. 6-283403) to control the position in the optical axis direction and the inclination of a table or a stage holding a wafer so that the wafer surface constantly coincides with an image plane (within the focal depth of the image plane) of the projection optical system in the exposure area.
Further, with the stepper or the scanner and the like, wavelength of exposure light used with finer integrated circuits is becoming shorter year by year, and numerical aperture of the projection optical system is also gradually increasing (larger NA), which improves the resolution. Meanwhile, due to shorter wavelength of the exposure light and larger NA in the projection optical system, the depth of focus had become extremely small, which caused a risk of focus margin shortage during the exposure operation. Therefore, as a method of substantially shortening the exposure wavelength while substantially increasing (widening) the depth of focus when compared with the depth of focus in the air, the exposure apparatus that uses the liquid immersion method has recently begun to gather attention (refer to, for example, the pamphlet of International Publication No. 2004/053955).
However, in the exposure apparatus using this liquid immersion method or other exposure apparatus whose distance (working distance) between the lower end surface of the projection optical system and the wafer is small, it is difficult to place the multipoint AF system in the vicinity of the projection optical system. Meanwhile, in the exposure apparatus, in order to realize exposure with high precision, realizing surface position control of the wafer with high precision is required.
Further, with the stepper or the scanner or the like, position measurement of the stage (the table) which holds a substrate (for example, a wafer) subject to exposure is performed in general, using a laser interferometer having a high resolution. However, the optical path length of the laser interferometry beam which measures the position of the stage is around several hundred mm or more, and furthermore, due to finer patterns owing to higher integration of semiconductor devices, position control of the stage with higher precision is becoming required. Therefore, short-term variation of measurement values which is caused by air fluctuation which occurs due to the influence of temperature fluctuation or temperature gradient of the atmosphere on the beam optical path of the laser interferometer can no longer be ignored.
Accordingly, in the case of performing position control of the table in an optical axis direction and in a tilt direction with respect to the plane orthogonal to the optical axis, including focus leveling control of the wafer during exposure, based on measurement values of the interferometer, it is desirable to correct measurement errors caused by air fluctuation and the like of the interferometer by some sort of method.